1. Field of the Invention
This invention relates to a melting cast installation in which metals of various kinds and in various forms, such as granular sponge titanium, granular hardners or cutting scraps of metals made in various machining processes, are continuously molten as raw materials and then continuously solidified, being reformed into ingots of various metals such as titanium, alloys thereof and so on.
2. Description of the Prior Art
In a melting cast installation according to the prior art, the molten pool of metal, made in a melting furnace by melting raw material, is poured into a melting pot for continuous casting and these operations are repeated every time when the molten pool of metal prepared at one time has completely been processed. It is, therefore, a serious problem that the speckles due to the inhomogeneity in the constitution of produced ingots result in deterioration of products.
The applicants considered a process consisting of sending continuously raw material for melt to a melting furnace, continuously melting the raw material in the melting furnace and obtaining ingots by solidifying molten pools according to the order of their production. As an apparatus for performing such process, they considered a combination of a melting furnace provided with a belt conveyor for sending the raw material to the melting furnace and plasma torches for melting the sent raw material and of a casting apparatus for solidifying molten pools of raw material.
The above described raw material for melt is generally a composition of a great variety of elementary materials. They are of every sort and kind in size, volume and specific gravity such as spongy or lumped. They are also different in forms such as granular or linear.
The above described raw material for melt is itemized into batches of a prescribed amount of raw material, which are transferred one after another to the melting furnace on the belt conveyer. However, a batch of raw material while being transferred on the belt conveyer, is mixed mutually with front and rear adjacent ones due to vibration generated by the belt conveyer and, consequently, changes the composition of elementary materials in respective batches. Furthermore, a locally uneven disposition of the elementary materials takes place, even with respective batches. For example, an elementary raw material of larger specific gravity is collected in a lower layer and that of a smaller specific gravity is disposed in an upper layer. As a result, when such batches of raw material are molten in the melting furnace, the quality of the molten pool of raw material varies successively according to the above described variation of the composition and the organization of an obtained ingot becomes irregular along the growing direction thereof. Furthermore, the molten pool of raw material at each time is different in quality from point to point due to the spatially uneven disposition of the different elementary materials and the organization of the ingot also becomes uneven in the direction of its thickness.
In addition, when the raw material is molten in the melting furnace, regions are produced which become molten more rapidly or more slowly since a very straight plasma arc extends from a plasma torch. Also, due to this situation, the quality of the molten pool varies spatially, resulting in the irregular organization of the ingot.
Applicants also considered utilization of a screw conveyor instead of the above described belt conveyer. However, since the raw material for melt includes a material apt to be caught, such as wires, it maybe tangled between a cylinder and a screw of the screw conveyer, stopping the operation thereof. The melting and casting of the raw material is therefore interrupted during the restoration of the belt conveyer and consequently, there appear irregularities in the organization of the ingot.